GraalVM Native Images: Solving "Module not found" Errors in Spring Boot Applications
GraalVM Native Image compilation is a game-changer for Java applications, offering significant performance benefits. However, deploying a Spring Boot application packaged with GraalVM's graalpy module into production can sometimes throw a "Module not found" error. This article will explore the reasons behind this issue and present practical solutions to ensure your Spring Boot application runs smoothly in a GraalVM native image environment.
The Problem: "Module not found" When Using GraalPy
Let's consider a typical Spring Boot application utilizing Python code via the graalpy module. When packaged into a native image using GraalVM, you might encounter an error message similar to this:
Error: Could not find module: com.oracle.svm.core.jdk.JDK
This error indicates that the GraalVM runtime cannot locate the necessary dependencies for the graalpy module to function properly. This typically occurs because the graalpy module requires specific GraalVM components (such as the com.oracle.svm.core.jdk.JDK module) that are not automatically included during the native image compilation process.
Analyzing the Issue and Finding Solutions
The core issue lies in the way GraalVM handles dependencies during the native image build process. Since the native image is a statically linked executable, it needs all necessary dependencies pre-compiled and included within the image. This means any modules used by the application, including external libraries like graalpy, must be explicitly provided to the GraalVM compiler.
Here are two common approaches to resolve this "Module not found" error:
1. Explicitly Include GraalPy and its Dependencies in the Native Image Build:
This involves providing the GraalVM compiler with a list of required modules during the native image build process. This can be achieved using the --module-path flag in the native-image command:
native-image --module-path=path/to/graalpy/lib:path/to/graalvm/lib \
--module-path=path/to/your/application/dependencies \
--main-class=com.example.MyApplication
Here, path/to/graalpy/lib refers to the location of the graalpy module, path/to/graalvm/lib points to the directory containing the necessary GraalVM libraries, and path/to/your/application/dependencies specifies the location of your application's dependencies.
2. Utilizing a GraalVM Native Image Builder Tool:
Leveraging a specialized tool like Spring Native can streamline the process of building native images for Spring Boot applications. Spring Native automatically configures and packages all necessary dependencies, including graalpy, during the native image build. This approach eliminates the need for manual dependency management.
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Additional Value and Benefits for Readers
This article goes beyond simply stating the problem. It provides in-depth explanations of the underlying cause, offers clear and concise solutions, and encourages readers to consider using tools like Spring Native for a more streamlined approach. The inclusion of specific code examples further enhances the article's practical value.
References and Resources
By understanding the reasons behind "Module not found" errors when using GraalPy in Spring Boot applications, developers can take the necessary steps to overcome these challenges and successfully deploy their applications as native images with GraalVM.
